Two more H7N9 influenza cases were reported in China today, including the first one from Zhejiang province in 2 weeks, as health groups weighed in with risk assessment updates and experts from China suggested a new way to get a jump on H7N9 and other novel viruses.

The newly confirmed infection from Zhejiang province, which last reported a case on Feb 12, involves a 2-year-old girl who is hospitalized with a mild illness, according to a provincial health department statement translated and posted by FluTrackers, an infectious disease news message board. Zhejiang province has the most H7N9 cases of any in China and has played a pivotal role in both outbreak waves.

The other new case involves a 65-year-old woman from Guangdong province who is hospitalized in critical condition, according to an official statement translated by FluTrackers.

The new cases lift the two-wave H7N9 outbreak total to 373, with 114 as the unofficial number of deaths. So far 237 illnesses have been detected in the outbreak's second wave, which began in October, compared with 136 in the first wave last spring.

Risk assessment updates

In other developments, the European Centre for Disease Prevention and Control (ECDC) and the Public Health Agency of Canada (PHAC) addressed the H7N9 threat in separate risk assessments.

The ECDC's assessment came in a broader risk assessment of human avian influenza A infection in China, dated Feb 24. The PHAC posted its updated H7N9 risk assessment today.

The ECDC assessment summarized H7N9 events as of Feb 18, and since then, cases have continued to taper off. However, it said the brisk pace of human infections that marked the second wave might point to a larger wild or domestic bird reservoir, an increase in the number of exposed people, increased transmissibility of the virus, a seasonal pattern, or a combination of factors.

Meanwhile, the PHAC risk assessment update covers H7N9 developments in China through yesterday. The agency noted that poultry and environmental samples have been found in all areas that reported human cases, except for Jilin province and Beijing.

The PHAC noted that, in the second wave, cases appear to be less skewed toward older adults, though more infections continue to be detected in males. Seven pediatric cases were reported in January, three of which involved mild illnesses, and so far no unusual clinical presentations have been reported, the agency said.

So far, the virus doesn't spread easily among people, though limited person-to-person transmission may occur when there is close contact, the update noted. The H7N9 virus bears close watching, though, because less severe cases have been seen in influenza-like illness surveillance, and the PHAC said it expects more cases to be reported as the flu season progresses.

Experts eye H9N2 control

In scientific developments, researchers from China today suggested that H9N2 avian flu appears to be an "incubator" for flu viruses of wild bird origin and that culling poultry infected with H9N2 might be an effective strategy for curbing the infections in humans. The team published its analysis online in The Lancet.

They wrote that H7N9, plus H10N8—another novel avian flu virus that recently sickened three people, two fatally in China's Jiangxi province—have a similar genetic lineage, which includes internal genes from H9N2 viruses in poultry. Reassortment between poultry H9N2 viruses and viruses from wild birds could trigger adaptation to domestic hosts, they observed.

"Poultry, especially in live markets, would have a pivotal role during the emergence of a novel influenza virus of avian origin," the group wrote.

Since many avian flu viruses in poultry can infect people, it’s impossible to predict the next one that will cause an outbreak in humans, the authors said, so focusing on H9N2 control might allow officials to prevent the next event.

They called on health officials to shutter live-poultry markets or periodically disinfect the establishments in China and other countries that have live-poultry markets.